Stability of beverage Stability of beverage emulsionsemulsions

By: Nooshin Noshirvani

BEVERAGE EMULSIONSBEVERAGE EMULSIONSOil-in-water emulsionsare prepared by dispersing flavor or

vegetables oils in a water phasedispersed oily phase :comprised of

essential oil, vegetable oil, and weighting agents [brominated vegetable oil (BVO), sucrose acetate isobutyrate (SAIB), ester gum (EG), and damar gum (DG)]

continuous phase: containing water, gum Arabic or modified starch, citric acid, preservatives, sugar and colors

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““cloudy” appearancecloudy” appearance

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Physical instabilityPhysical instability of beverage of beverage emulsionsemulsions

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Instability (Creaming) rateInstability (Creaming) rate

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Oil phase volume fraction

Beverage emulsion stabilityBeverage emulsion stability

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Beverage emulsion stabilityBeverage emulsion stability

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homogenizationhomogenization Weighing agents

Weighing agents

hydrocolloids

hydrocolloids

Weighing agentsWeighing agents

(density-adjusting agents)lipophilic compounds with specific gravity higher

than that of waterbrominated vegetable oil (BVO) d:1.23–1.33

g/cm3 sucrose acetate isobutyrate (SAIB) d: 1.146

g/cm3ester gum (EG)damar gum (DG)restricted use

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15ppm15ppm

300 ppm300 ppm

adjustment of density of the oilsadjustment of density of the oils

Pearson rule

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to adjust the emulsion’s density in order to minimize phase separation of beverage emulsions

Weight of weighting

agent/weight of oil mixture

Weight of weighting

agent/weight of oil mixture

Specific gravity of weighting

agent

Specific gravity of weighting

agent

specific gravity ofweighting oil

specific gravity ofweighting oil

Effect of phase composition on Effect of phase composition on cloud appearancecloud appearance

The oil is the most important ingredient for providing the cloudy appearance and turbidity

Particle size of oil droplets plays a major role in beverage emulsion stability

increasing the level of oil could raise the cloudy appearance due to the scattering a larger fraction of light

at restricted concentration of weighting agents

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Effect of oil concentration on Effect of oil concentration on cloudy appearancecloudy appearance

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4.3 4.3

Particle size of oil dropletsParticle size of oil droplets

Result of the interplay between droplet fragmentation and droplet coalescence during homogenization

As the homogenization pressure increases, the droplets become less resistant to the deformation and fragmentation.

The use of high pressure homogenization has been effective for the production of emulsions containing the narrowly distributed particle size with a mean size ranging from 200 nm to 5 μm

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Water phase componentsWater phase components water-soluble polysaccharides stabilizer viscosity adjuster film formation steric hindrance electrostatic interaction

The widely used hydrocolloids gum Arabic modified food starch gum tragacanth propylene glycol alginate xanthan gum Pectin gellan gum guar gum carboxymethylcellulose corn fiber gum

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Amphiphilic characterit must contain numerous and accessible hydrophobic groups to enable the adsorbing molecules to adhere to the interface and protect the droplets from coalescing

Amphiphilic characterit must contain numerous and accessible hydrophobic groups to enable the adsorbing molecules to adhere to the interface and protect the droplets from coalescing

Stabilization mechanismsStabilization mechanisms

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Steric stabilizationSteric stabilization

gum Arabic or modified starch in combination with xanthan gum

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Stability with hydrocolloidsStability with hydrocolloids

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Stability with modified starchStability with modified starch

Octenyl-succinated starch or octenyl succinate anhydrate (OSA)

esterification of starch with anhydrous octenyl-succinic acid under alkaline conditions.

Consists amylopectin that contain non-polar side-groups

Purity Gum is mildly anionic in aqueous solutions

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Gum arabicGum arabic

an effective emulsifier because of:High water solubility,Low solution viscosityGood surface activity,(consist of branched

arabinogalactan blocks attached to a polypeptide backbone)

Ability to form a protective film around emulsion droplets

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Stability with Arabic gumStability with Arabic gum

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Stability with surface active Stability with surface active moleculesmolecules

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Molecular characteristics of the Molecular characteristics of the adsorbed biopolymeradsorbed biopolymer

play the dominant role in long-term stability of emulsion

Using biopolymers such as gum Arabic or modified starch in combination with xanthan gum to stabilize the beverage emulsions sterically have shown potentials

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Rheology of water phaseRheology of water phase

addition of 0.3% (w/w) xanthan gum into the water phase containing modified starch could retard the breakdown of the emulsions through change in rheology of water phase.

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Physical properties of orange Physical properties of orange drink emulsionsdrink emulsions

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Unstable

Unstable

StableStable Moderately

stable

Moderately

stable

More Newto

n

More Newto

n

The rate of droplet coalescenceThe rate of droplet coalescence

Dc: rate of droplets coalescence, D0 and Dt are the mean droplet sizes initially and at time t, Dc :can be determined by plotting 3(ln (Dt/D0) vs. time (t).

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The rate of droplet coalescenceThe rate of droplet coalescence

Lowest stability

Highest stability

loss of emulsification

capacity at low pH (pH=3)

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residual

surface activity

residual

surface activity

time evolution of the light time evolution of the light transmission for emulsionstransmission for emulsions

Slower sepration

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Shelf stability of emulsions in Shelf stability of emulsions in orange juice drinkorange juice drink

Unstable

loss of emulsification capacity of Arabic gum at low pHgreater aqueous phase effective volume higher molecular weight more open structure of gum Arabic

stablestable

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Gum arabic and modified starch have relatively low surface activities (compared to proteins or surfactants)

a large excess must be added to ensure that all the droplet surfaces are adequately coated

a large excess of nonabsorbed polysaccharide in the aqueous phase of emulsions

nonabsorbed biopolymers are capable of promoting droplet flocculation through a depletion mechanism

Flocculation causes a number of effects that are detrimental to emulsion quality:

1. enhanced creaming due to the increase in particle size2. decreased cloudiness due to the increase in particle size 3. enhanced coalescence because droplets are brought

into close proximity 29

Disadvantages of Disadvantages of hydrophobic hydrocolloidshydrophobic hydrocolloids

The degree of flocculationThe degree of flocculation

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Dependence of viscosity on Dependence of viscosity on biopolymer concentrationbiopolymer concentration

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2- 3 times larger effective volume

The influence of hydrocolloid The influence of hydrocolloid on creamingon creaming

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The CFC of the emulsions also depended on droplet size, decreasing as the droplet radius increased.decreasing the droplet size can reduce the susceptibility of an emulsion to flocculation.

0.40.4

1.71.7

Dependence of critical flocculation Dependence of critical flocculation concentration (CFC) on droplet sizeconcentration (CFC) on droplet size

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strength of the depletion attraction increases with droplet size, therefore less biopolymer is required to induce flocculation for larger droplets

strength of the depletion attraction increases with droplet size, therefore less biopolymer is required to induce flocculation for larger droplets

ConclusionConclusion

increase in oil concentration affect the opacity and showed that oil content is highly responsible for the opacity of emulsions and hence in the final product

the conventional method for stabilization of beverage emulsions were explained

at elevated level of oil and regulated level of weighting agents, practically, the density of oil phase cannot be adjusted to the target levels.

The importance of particle size distribution and rheological properties of water phase and emulsions on stability of beverage emulsions were highlighted.

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ConclusionConclusionThe modification of rheological characteristic of

continuous aqueous phase can play an important role in relation to the storage stability of beverage emulsions.

When the steric stabilization is dominant, the type of hydrocolloid, concentration, and combination are responsible for rheological properties of emulsions and stability of cloud in orange beverage.

Hydrophobically modified starches have been identified as 1 of the most promising replacements for gum arabic 35

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